A conventional gravity operated flush toilet has several basic components. The china components include a bowl and a tank mounted atop a rear portion of the bowl. The bowl and tank may either be separate pieces or may be molded as a single unitary piece. The plumbing components of the conventional gravity operated flush toilet include a fill valve in the tank that is connected to a water supply line, a flush valve mounted in a hole in the bottom wall of the tank that communicates with the bowl, a flapper valve that normally closes the flush valve, and a lever or push button on the outer wall of the tank that is connected with a chain or other mechanical linkage for momentary lifting of the flapper valve. This allows water stored in the tank to flow rapidly through the flush valve into the bowl to carry waste along with the water through a trap connected to the underside of the bowl and into a waste pipe connected to a sewer line, septic tank or other waste reservoir.
Conventional flush valves for gravity operated toilets are well known in the art. Such flush valves are generally cylindrical and provide a round valve seat for the liftable flapper valve. They are secured within a drain hole located in the bottom wall of the toilet tank from underneath the bottom wall. Typically a large nut is screwed over a male threaded lower portion of the cylindrical flush valve body, on the underside of the bottom wall of the tank. Extending upwardly from and to one side of the flush valve itself is a cylindrical overflow tube. The purpose of the overflow tube is two-fold. First, the overflow tube prevents flooding in the case of water overflow to the tank. The overflow tube thus ensures that a proper water level is maintained within the toilet tank in the condition of overflow. Ideally, the inlet of the overflow tube is set at a point where it is slightly above normal water level, but below the bottom of the flush lever nut that is located on a vertical wall of the tank for actuation of the flushing cycle. The second purpose is that the overflow tube serves as a conduit to the toilet bowl during refilling of the tank, a small amount of water flowing to the tank being diverted through the overflow tube for this purpose. This occurs when the fill valve is re-filling the tank and, via the overflow tube, the toilet bowl, the toilet bowl having been emptied during the siphoning of the water in it during the flushing action.
In the design of the conventional flush valve, this overflow tube is a vertically-extending circularly-tubular structure having a generally vertical axis. The flush valve itself is similarly a vertically-disposed circular structure having a generally vertical axis and also having a central aperture that is greater inner diameter as compared to the diameter of the overflow tube, the flush valve aperture having a cylindrical valve seat defining an inlet at its uppermost portion and an outlet at its lowermost portion. In this configuration, a flow passageway is defined at the bottommost portion of the overflow tube whereby a water flow continuum is created between the overflow tube, the central passageway and the outlet of the central aperture of the flush valve. Water flowing into the overflow tube from the tank flows down the overflow tube, then flows out of the tube at the passageway that is typically disposed at a right angle from the overflow tube, into the central aperture of the flush valve, and then flows through the flush valve outlet. In this configuration, the bulb of the flapper valve can severely restrict the overflow capacity of the flush valve by impinging on the flow area around the bulb, including the passageway between the overflow tube and the flush valve outlet. This becomes especially critical when an original equipment manufacturer (OEM) flapper is later replaced with a new flapper, typically manufactured by another company, to some rather arbitrary specifications. The problem is that adequate overflow capacity is completely overlooked, because the only issue in the consumer's mind is typically how to stop the flapper from leaking. If the passageway between the overflow tube and the flush valve outlet is blocked, even in part, by the flapper valve bulb, then the ability of the overflow tube to do its job is compromised. The flush valve of prior art is also rather difficult to mold as a one-piece item using conventional plastic molding processes.
In the view of these inventors, what is needed is a flush valve having an outlet from the central aperture that is offset from its conventional position. This configuration would place the outlet portion of the central aperture of the flush valve partly underneath the overflow tube, thereby improving overflow capacity of the flush valve. This configuration could also make the flush valve a more compact device, while also making it a high overflow capacity device. The flapper valve seat, or the cylindrical valve seat of the flush valve at the flush valve inlet, would retain its cylindrical shape so as to allow flapper valves of current manufacture to be used with the device. But the axis of the flush valve would be modified. At the inlet of the flush valve, the axis would be directed at somewhat of an angle relative to the vertical at the uppermost portion of the flush valve. At the outlet and at the lowermost portion of the flush valve, the axis would return to vertical. In this way, the lowermost portion of the flush valve would be disposed both below a portion of the overflow valve and below the inlet of the flush valve.
In the view of these inventors, this configuration would also make the device easier to mold. For example, the flush valve described above would eliminate the requirement of molding the lateral section of the passageway through the valve body separately, thus simplifying the mold process, reducing costs, and increasing the durability of the mold. In the conventional molding process, complicated retracting mold cores are required to be used to form the passageway. These disadvantages are avoided by offsetting the outlet of the flush valve such that the core for the bottom of the valve body and the core mold for the overflow tube meet such that an extra horizontal, or lateral, connection, or self-retracting core is not required.
It should also be mentioned that, in the United States, there are two basic markets for toilet flush valves, namely, the OEM market and the after-installation market. The former consists of large toilet manufacturers that assemble and sell complete gravity operated flush toilets including flush valves. The latter consists of hardware and plumbing supply stores that sell to plumbers and home owners for repair and replacement in toilets already installed in residences. Accordingly, it would be desirable to provide the offset outlet flush valve of the present invention in configurations that would allow it to be used in both the OEM and the after-installation markets.
Finally, it is recognized that every gravity operated flush toilet has an optimum fill level that ensures that enough water is in the tank for proper flushing without wasting water or risking incomplete waste carry out. For many years, gravity operated flush toilets in the United States had tanks with capacities of three and one-half, five gallons, or more. More recently, the Environmental Protection Agency (EPA) has mandated that low water consumption toilets be installed in all new construction and during all re-models, with a maximum water usage of 1.6 gallons per flush. Both the older high volume gravity operated flush toilets and the newer low volume gravity operated flush toilets come in a wide range of tank configurations with different optimum fill levels. Because of this, installation of after-market flush valves, which are manufactured in a pre-determined height to accommodate the deepest tank depth likely to be found, typically requires the installer to hand cut the overflow tube of the flush valve to fit. In the experience of these inventors, it would be unduly expensive to manufacture a variety of different overflow valves, each having an overflow tube of different height, to satisfy the configurations of the various gravity operated flush toilets manufactured in the United States and abroad. It is, therefore, advantageous to provide the after-installation offset outlet flush valve that is constructed in accordance with the present invention with an adjustable overflow tube that would permit plumbers and do-it-yourself homeowners to install the offset outlet flush valve and to adjust the height of its overflow tube as necessary.